[tech] VGA to TV DVD output quality

Discussion in 'Desktop & Laptop Computers Forum' started by starless, Feb 21, 2005.

  1. starless

    starless
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    Hi, I noticed (like anyone, I suppose) that playing a DVD movie on a standalone DVD player connected to a TV set you get a much better quality than playing the same DVD on a computer connected to the same TV through the TV-out of your video card.

    With "better quality" I mean better image definition, and better color rendering (the latter could be due to poor software decoding, but looks fine on the monitor screen, so that's strange).
    I'm talking about cheap PC hardware: the composite video output of an old GeForce2MX, or the composite and s-video outputs of an Apple iBook, using the Apple miniVGA->TV adapter. It's cheap hardware, but it should have enough bandwidth anyway to beat a composite video connection between a cheap standalone DVD player and the TV, at least; while it does not.
    And I'm talking about PAL systems.

    Can anyone kindly explain me the reason for this, or maybe point me to some online resource explaining this? I'd expect this to be some kind of FAQ...
    Thanks in advance.
     
  2. Werner

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    it is simply because the board manufacturers have never bothered about dvd quality in the past. ALL reviews have always focused on speed speed speed and the fastest wins. It is only in recent months that IQ has taken a more prominent role

    The never nvidia graphics cards, coupled with the appropriate drivers will enable the video processing engine on the 6600 and 6800, and you can see a marked difference then.


    But for older cards, the market has always said "the faster one is better" and because of this they made faster cards, not bothering about image quality too much.

    you may sau, it is our own fault for not complaining loudly enough
     
  3. starless

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    Thanks Werner, but how is it, then, that image quality is very good on the computer monitor (which even has a higher definition than TV), and deteriorates only when brought to TV?
    This makes me think that it is not a problem of "image quality" in a general way like you suggest; it only seems to be limited to VGA->TV conversion, which not necessarily is a feature built in the video card by the card manufacturer...
     
  4. Werner

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    yes, it is a feature of the "graphics card" as a whole, although the job is done by a seperate tv encoder chip. the tv encoder chip can easily be of dubious quality, but garbage in=garbage out, so it the actual vga chip on the board isnt so hot at sending the data to the tv encoder, quality will suffer even more.

    either way, one manufacturer makes a vga card (e.g. asus, gigabyte etc) and they are responsible for the quality of all the components on that card. pick rubbish tv encoder (or, perhaps a "good" one doesnt even exist to pick from) and the output will not be up to scratch
     
  5. probedb

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    Plus it's normally S-Video out for the TV out whereas you'd normally watch a DVD player via an RGB SCART or component. Then there's the fact that the gfx card is encoding a resolution down to TV size whereas a standalone DVD player works at PAL/NTSC resolution to start with.
     
  6. DaveP

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    There is a new graphics card manufacturer that does give far superior quality when attached to a TV. Not only is it good it's also cheap (well, in the states anyway) This is it but I cannot find a UK retailer.

    Dave
     
  7. starless

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    Thanks everyone.
    So, you are saying that the problem is not the VGA standard itself, but mostly the TV encoders found in common video cards instead?

    Do you agree that VGA output (e.g. 800x600 24bit 100Hz, just to pick something slightly resembling PAL) is superior to the PAL TV standard? I mean: VGA could theoretically produce much better images than PAL, right?

    If so... then, if I took my VGA output and brought it to my TV via a theoretical wonderful VGA->RGB converter (does a really good one exist?), would it be possible to get a really good picture, comparable to a standard DVD player one?

    I do not want to actually do it, it would probably be more expensive than a good DVD player; ;) I just want to understand something I'm missing...
     
  8. DaveP

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    If you are handy with a soldering iron you could have a go at making a VGA to RGB Scart lead yourself.

    There are several posts about it.

    Of course, you may blow your TV up, or your PC, or even both! But hey, what's life without a few risks!

    Dave
     
  9. probedb

    probedb
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    VGA is just the connection, nothing to do with the resolution/refresh rate etc. Although on PCs VGA resolution is 640x480 (sigh, those were the days ;) ). But yes [email protected] would be better than PAL provided the display supports the res and refresh rate you want.

    That's why we're going to HDTV, HDTV res can be 1920x1080 or 1280x720 both interlaced and progressive...it wipes the floor with PAL's 720x576 (?) res obviously as there's more detail but you need a display that will support it :)
     
  10. starless

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    Thanks pinkprobegt, I was asking because I know someone who essentially says that TV out from a computer is crap because "PAL is better than VGA and has more bandwidth", and that a PAL signal resulting from a converted VGA signal cannot be as good as the PAL signal coming from a standalone DVD player, which sounds strange to me. Do you agree?

    Thanks DaveP, but I don't think I'm going to do any dangerous tests. ;) As I already wrote, I was only looking for come clarifications on the theoretical side of things.
     
  11. probedb

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    I think your friend has got a bit confused, bearing in mind most modern graphics cards will do resolutions like 2048x1536 @ 60hz and 24 bit colour :) And that's over the VGA connection.
     
  12. Loftus

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    The DVD player is outputing to native PAL/NTSC resolution. Your Video card will (mostly likely) be outputing a "computer-based" resolution which the TV encoder has to down-sample to fit in a PAL/NTSC format signal.

    If you can eliminate the PC->TV down-sampling, that can help a LOT (i.e. set the windows resolution to that of PAL/NTSC). I would recomend Googling "TV Tool". I had a great deal of sucess improving the quality of my htpc's TV-output.

    Or if you're really serious you could upgrade your telly to a plasma/LCD that has a VGA (or similar) input and never have to worry about TV encoders again :cool:
     

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